Why is my finger locking?

[erin_fuss_]

Recently, my finger ring finger on my left hand started to hurt. There is no sign of swelling or bruising. When I'm bending it, it will make a popping sensation. Sometime when I put my hand into a fist and try to open it, all my fingers but my ring finger will move up. And can try as hard as I can but I can't get it to move without touching it for a while. But if someone pushes it back up, they feel no resistance. Same if I move it with my other hand.